When performing a 64-bit sra of a negative value with a shift range from
[32-63], create the hi-half with a move of -1.
Alive verification: https://alive2.llvm.org/ce/z/kXd7Ac
Also, preserve exact flag. Alive verification:
https://alive2.llvm.org/ce/z/L86tXf.
---------
Signed-off-by: John Lu <John.Lu@amd.com>